13. b2b3 Another subtle move. The path of the bishop is open to a3, and this will be quite useful. 13... e8c8 The king goes to the wrong side of the board. More than anything, this is a positional mistake: White's attack is simply much faster. 14. c1d2 The human reaction, simply preparing b4-b5 and mate. 14... c8b8 After castling queenside, Kb8 is the first move that should be considered. 15. b3b4 